JPH0526988A - Life detecting apparatus for secondary battery - Google Patents

Abstract

PURPOSE:To detect the life of a secondary battery automatically. CONSTITUTION:At first, a secondary battery 12 is discharged through a discharging block 30 until the terminal voltage of the battery becomes equal to a discharge terminating voltage. Then a switch SW2 is switched to the charge side. A switch SW1 in a charging block 20, the discharging block 30 and the switch SW2 are controlled with a control circuit 41. The secondary battery 12 is fully charged by the quick charge of a -DELTAV method. Then, the time until the voltage of the secondary battery 12 which is fully charged is lowered to the discharge- termination voltage through the discharging block 30 is measured with a discharge time measuring circuit 43. When the measured time is shorter than the specified required time, the control circuit 41 turns ON an LED 42 so as to show the fact that the life of the secondary battery 12 is terminating to the user.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary battery life detecting device for automatically detecting the life of a secondary battery.

[0002]

2. Description of the Related Art Secondary batteries such as nickel-cadmium batteries (Ni-Cd batteries), nickel-hydrogen batteries, lithium secondary batteries, and lead batteries are economical because they can be charged and used. Since it is easy to reduce the weight,
At present, the demand for portable, compact and lightweight power sources such as notebook PCs, notebook word processors, handy terminals, mobile phones, and electric shavers is rapidly increasing.

The life of the secondary battery as described above is based on JIS
(Japanese Industrial Standards), for example, Ni-C
In the case of d battery, it is specified by JIS C 8705 standard, and the condition is that some charging and discharging are performed by the method specified by JIS, and the actual capacity is 60% of the nominal capacity.
It is represented by the number of times of charging and discharging (charging and discharging cycle) until it drops to 500. The charging and discharging cycle is 500 cycles.

[0004]

However, in practice, the usage conditions of the secondary battery differ depending on various factors such as the load current of the equipment used, the charging device, and the ambient temperature of the usage. The battery life is not uniquely determined by the charge / discharge cycle defined by JIS standard.
In other words, in practice, it is difficult to define the actual life of the secondary battery used under various usage environments with a fixed number of charge / discharge cycles. However, due to the above reasons, the operating time of the rechargeable battery in the conventional charging device varies depending on the usage environment. There is no function of notifying the user (user) of the time when the above condition is no longer satisfied, that is, the life of the secondary battery. For this reason, the user cannot know at all when the battery capacity of the secondary battery will not satisfy the specification value, except by actually using it. It may be inconvenient, such as when it does not work, which is a problem.

This problem is that the conventional charging device for a secondary battery does not have a function of detecting that the battery capacity of the secondary battery to be charged has decreased until it does not satisfy the specification value.
Therefore, it is because the user cannot be notified that the secondary battery has reached the end of its life.

Therefore, if the lifespan of the secondary batteries can be automatically detected, the battery capacities of all the secondary batteries having different usage environments will not meet the specified value due to the end of the battery life. It is considered that the user can be notified of the decrease and the user can easily confirm the replacement time of the secondary battery.

An object of the present invention is to make it possible to automatically detect the life of a secondary battery.

[0008]

The means of the present invention are as follows. The charging means 1 (see the block diagram of FIG. 1) fully charges the secondary battery by various charging methods (for example, -ΔV detection method). The discharging means 2 is provided with a discharging resistor or the like,
The secondary battery completely charged by the charging means 1 is discharged until the terminal voltage thereof drops to a predetermined voltage (for example, the discharge end voltage as described in claim 2). The time measuring means 3 measures the time (discharge time) from when the discharging means 2 starts discharging the secondary battery until when the discharging ends.
The notification unit 4 determines whether or not the secondary battery has reached the end of its life by estimating the remaining battery capacity of the secondary battery based on the discharge time measured by the time measurement unit 3, and the like If it is determined that, for example, LED
(Light emitting diode) is turned on, a message is displayed on the LCD (liquid crystal display device), or a buzzer sounds to notify the outside.

[0009]

The operation of the means of the present invention is as follows. First, the charging means 1 fully charges the secondary battery. When performing this complete charging, it is preferable that the secondary battery is once discharged to the discharge end voltage by the discharging means 2 and then charging is started in consideration of the characteristics of the secondary battery. Then, the fully charged secondary battery is discharged by the discharging means 2 until the terminal voltage thereof drops to a predetermined voltage (for example, discharge end voltage). The time measuring means 3 starts measuring time from the time when the discharging means 2 starts discharging the secondary voltage, and continues the time measurement until the time when the discharging means 2 finishes discharging the secondary voltage. The notification means 4 inputs the discharge time of the secondary battery measured as described above from the time measuring means 3, and based on the discharge time, the battery capacity of the secondary battery is already lower than the specification value. Yes, that is, determine whether the secondary battery has already reached the end of its life,
When it is determined that the life has ended, the fact is notified to the outside by lighting an LED (light emitting diode) or the like. Therefore, the life of the secondary battery can be automatically detected.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment will be described below with reference to FIGS. FIG. 2 is a block diagram showing the system configuration of a battery charger with a battery life detection function.

As shown in the figure, the above charging device is a charging device for completely charging a secondary battery 12 made of a Ni-Cd battery mounted in a predetermined housing of the device through a charge / discharge switching switch SW2. The block 20, the discharge block 30 for discharging the secondary battery 12 through the charge / discharge changeover switch SW2, the charge block 20, and the discharge block 30 are controlled to charge the secondary battery 12 by quick charging or trickle charging. Charge / discharge control block 4 for fully charging and discharging to the discharge end voltage before the complete charging
0 and the charge / discharge changeover switch SW2.

The charging block 20 is for rapidly charging the secondary battery 12 by the -ΔV method (minus delta V method), and at the end of charging of the secondary battery (Ni-Cd battery) 12, the battery voltage is changed. After reaching the maximum value (hereinafter, referred to as a peak value), the falling voltage (-ΔV: minus delta V) is detected and the charging is completed (the secondary battery 12 is fully charged). The detection of -ΔV includes a comparator 23a and a peak value storage circuit 23b that adds the peak value of the secondary battery 12 as a comparison reference voltage to one input terminal (+ input terminal) of the comparator 23a. This is performed by the detection circuit 23. During charging, the terminal voltage of the secondary battery 12 is applied to the other input terminal (-terminal) of the comparator 23a via the charge / discharge switch SW2. Also, the charging block 2
0 is the constant current i ₁ for rapid charging of the secondary battery 12 as well.
Alternatively, the constant current circuit 21 that supplies the constant current i ₂ for trickle charging, and the rapid charging constant current i ₁ output from the constant current circuit 21 when the secondary battery 12 is rapidly charged are supplied to the charge / discharge changeover switch SW2. When the secondary battery 12 is output and trickle charged, the constant current i ₂ for trickle charging is output.
Has a switch SW1 for quick charge / trickle charge switching (hereinafter simply referred to as changeover switch SW1) for outputting to the charge / discharge changeover switch SW2.

The discharge block 30 has one end grounded and the other end connected to the charge / discharge changeover switch SW2, and a discharge resistor 31 having a predetermined resistance value through which a discharge current flows when the secondary battery 12 is discharged; Charge / discharge switch SW
2 to a discharge end voltage detection circuit 32 for detecting a predetermined discharge end voltage (a terminal voltage of the secondary battery 12 at which the discharge should be stopped) in order to avoid overdischarge of the secondary battery 12. This discharge end voltage detection circuit 32 is used for the secondary battery 1
When it is detected that the terminal voltage of 2 becomes equal to the discharge end voltage, the detection signal d is output to the charge / discharge control block 40.

Finally, the charge / discharge control block 40
Is the output terminal of the comparator 23a of the −ΔV detection circuit 23 in the charging block 20 and the changeover switch SW.
1 and the charge / discharge changeover switch SW2, and controls the two changeover switches SW1 and SW2 to perform quick charge / trickle charge (compensation charge) and discharge of the secondary battery 12, and the battery of the secondary battery 12. A charge / discharge switching / LED control circuit 41 (hereinafter simply referred to as a control circuit 41 for convenience) that controls to turn on an LED (light emitting diode) 42 when the capacity drops below a specification value, and a fully charged secondary It comprises a discharge time measuring circuit 43 for measuring the time until the terminal voltage of the battery 12 drops to the discharge end voltage. The discharge time measurement circuit 43 is connected to the discharge end voltage detection circuit 32 in the discharge block 30 and the control circuit 41 in the own block 40, and starts measurement of the discharge time according to an instruction from the control circuit 41. The measurement of the discharge time is stopped by applying the detection signal d from the discharge end voltage detection circuit 32. The detection signal d output from the discharge end voltage detection circuit 32 is also input to the control circuit 41, and when the detection signal d is input, the control circuit 41 reads the measured discharge time from the discharge time measurement circuit 43, Based on the discharge time, the secondary battery 12
It is determined whether the battery capacity of is lower than the specification value.
In addition, the charge / discharge control block 40 includes the secondary battery 1 described above.
LE that informs the user that the life of 2 is over by lighting
In addition to D42, a battery life confirmation switch SW3 (hereinafter simply referred to as a confirmation switch for convenience) connected to the control circuit 41 for instructing the user whether to confirm the life of the secondary battery 12 or perform charging. (Described as SW3). The confirmation switch SW3 is an external switch operated by the user, and when the user sets it to ON (ON), the confirmation switch SW3 is set to OFF (OFF) to indicate that the secondary battery 12 is rapidly charged. It is possible to give an instruction to inspect the life of the battery 12. That is, the control circuit 4 of the charge / discharge control block 40.
When the confirmation switch SW3 is on, the on / off control 1 controls on / off of the charging / discharging changeover switch SW2 and the switch SW1 in the charging block 20 to fully charge the secondary battery 12 by quick charging or trickle charging. On the other hand, when the confirmation switch SW3 is off, the charging / discharging changeover switch SW2 and the changeover switch SW1 in the charging block 20 are also controlled to detect whether or not the battery capacity of the secondary battery 12 is lower than the specification value. To do.

Next, the operation of the charge detection device having the above configuration will be described with reference to the flowchart of FIG. The flowchart of FIG. 3 shows a life check operation of the secondary battery 12 (battery life check mode) and a full charge operation of the secondary battery 12 (charge mode) performed by the control of the control circuit 41 in the charge / discharge control block 40. It is a flow chart explaining operation of two modes.

Of the above two modes, the operation in the charging mode will be described first. When the control circuit 41 determines that the confirmation switch SW3 is set to OFF, that is, the user selects the charging mode (S1), the charging / discharging changeover switch SW2 is switched to the discharging side, and the secondary battery 12 is set. Discharge through the discharge resistor 31 in the discharge block 30 (S
3). During this discharge period, the discharge end voltage detection circuit 32 in the discharge block 30 constantly monitors the terminal voltage of the secondary battery 12, and when it detects that the terminal voltage has dropped to a predetermined discharge end voltage, The detection signal d is output to the control circuit 41. The control circuit 41 switches the charging / discharging changeover switch SW2 to the charging side by the input of the detection signal d, and stops the discharging of the secondary battery 12 (S4).

By the above operation, the secondary battery 12 is discharged until its terminal voltage drops to a predetermined discharge end voltage.
Subsequently, the control circuit 41 sets the changeover switch SW1 in the charging block 20 to the quick charging side, and supplies the secondary battery 12 with the constant current i ₁ for rapid charging output from the constant current circuit 21. During the charging period of the secondary battery 11, the peak value detection circuit 2 of the −ΔV detection circuit 23 in the charging block 20.
3b constantly monitors the terminal voltage of the secondary battery 12 via the charge / discharge changeover switch SW2, detects the timing when the terminal voltage of the secondary battery 12 changes from rising to falling, that is, the peak value, and detects the secondary value. The peak value of the battery 12 is captured and stored. During the charging period of the secondary battery 12, the latest terminal voltage of the secondary battery 12 is input to the − input terminal of the comparator 23a of the −ΔV detection circuit 23 via the charge / discharge switching switch SW2. Then, after the terminal voltage 12 of the secondary battery 12 reaches the peak value, the rapid charging by the constant current i ₁ as described above is continued, and the terminal voltage of the secondary battery 12 gradually decreases. A predetermined time after the peak value is reached, the terminal voltage is -ΔV from the peak value.
When the voltage decreases, the detection signal e indicating that the rapid charging is completed is output from the comparator 23a to the switch SW1, the control circuit 41 of the charge / discharge control block 40, and the discharge time measuring circuit 42. By the output of the detection signal e, the changeover switch SW1 of the charging block 20 is immediately switched to the trickle charging side, and the constant current i ₂ for trickle charging output from the constant current circuit 21 is supplied to the secondary battery 12. The trickle charging becomes possible (S8).

As described above, the secondary battery 12 can be repeatedly charged by discharging the secondary battery 12 once to the discharge end voltage and then performing rapid charging. The battery capacity gradually decreases, and eventually decreases to a value lower than the specification value. Also, its internal resistance gradually increases.

Therefore, in this embodiment, a battery life confirmation mode is provided so that the user can know that the battery capacity of the secondary battery 12 has dropped to a value lower than the specification value. The battery life confirmation mode is set by the user turning on the confirmation switch SW3 by an external operation.

Next, the operation of this battery life confirmation mode will be described.
It will be described with reference to the flowchart of FIG. 3 again. When the control circuit 41 determines in step S1 that the confirmation switch SW3 is set to ON, that is, the user selects the battery life confirmation mode, the control circuit 41 then proceeds to step S1 described above.
By the same control as in 8, the secondary battery 12 is fully charged by rapid charging (S2).

Subsequently, the control circuit 41 executes the above-described discharging process S3 to start discharging the secondary battery 12 via the discharging resistor 31 and at the same time causes the discharge measuring circuit 43 to start measuring the discharge time ( S5).

During the period of this discharge, the above-described process S4 is executed, and the discharge end voltage circuit 32 is operated by the charge / discharge changeover switch S
The terminal voltage of the secondary battery 12 is constantly monitored via W2, and when it is detected that the terminal voltage is equal to a predetermined discharge end voltage set in advance, the detection signal d is output to the charge / discharge control block 40. It outputs to the discharge time measurement circuit 43 and the control circuit 41 (S4).

As a result, the discharge time measuring circuit 43 stops measuring the discharge time. Then, the control circuit 41
Reads the discharge measurement time from the discharge time measurement circuit 43, and sets the discharge measurement time T to a predetermined reference time T _ref (the operation specification time of the secondary battery 12 is discharged with the discharge current value of the discharger). (S6), and if T ≧ T _ref , it is determined that the battery capacity of the secondary battery 12 is still sufficient, and the charging process S
8 is performed to fully charge the secondary battery 12. On the other hand, T <T
If it is _ref , the LED 42 is turned on, and the user is informed that the battery capacity of the secondary battery 12 has dropped to a value lower than the specification value and that it has already reached the end of life (S7).

As described above, in this embodiment, the secondary battery 12 is used.
As the battery approaches the end of its life, the internal resistance of the battery increases and the discharge time T decreases.
The life of the secondary battery 12 is detected by utilizing the characteristic of 2.

In the charger of the above embodiment, the secondary battery 1
2 quick charge is done by -ΔV method, but -ΔV
It is not applied only to a charger that performs rapid charging by the method, but it is a current reduction method, a temperature detection method (generated when the negative electrode Cd absorbs oxygen generated when the Ni-Cd battery is overcharged). Temperature rise due to heat of chemical reaction is detected by a temperature sensor to detect the charging stop time), or gas sensor method (Ni-Cd connected in series)
A third electrode for detecting oxygen gas is provided in advance in one cell of the battery group, and oxygen generated at the end of charging (charging of about 90%) is detected to detect the third electrode. The method can be applied to a charger that performs rapid charging by any other method, such as a method of controlling the charging current by the voltage that occurs at 1). Further, the present invention can be applied not only to the charger that performs the rapid charging as described above, but also to the charger of the standard charging method that performs the cycle charging with a moderate current. Further, it can also be applied to a charger that charges a secondary battery by the doit yourself charging method.

In addition to detecting the life of the secondary battery,
Detection of secondary battery defects such as cell shorts and memory effects
It can be easily applied to confirmation.

[0027]

Since the present invention can automatically detect the life of the secondary battery, the battery capacity of all the secondary batteries having different operating environments has decreased due to the end of the battery life until it does not satisfy the specification value. Can be notified to the user, and the user can easily confirm the replacement time of the secondary battery. Therefore, it is effective for a high-load electronic device with a short battery life and a charging device for an electronic device used at high temperature.

[Brief description of drawings]

FIG. 1 is a block diagram of the present invention.

FIG. 2 is a circuit block diagram showing a system configuration of a secondary battery life detecting device according to an embodiment.

FIG. 3 is a flow chart for explaining the operation of the above-mentioned embodiment performed by the control of the charge / discharge switching / LED control circuit.

[Explanation of symbols]

1 charging means 2 discharging means 3 hours measuring means 4 Notification means

Claims (2)

[Claims] 1. A charging means for completely charging a secondary battery, a discharging means for discharging the secondary battery fully charged by the charging means so that the terminal voltage of the secondary battery drops to a predetermined voltage, and the discharging means. On the basis of the discharge time measured by the time measuring means for measuring the time from the start to the end of the discharge of the secondary battery,
A secondary battery life detection, comprising: a notification unit that determines whether or not the secondary battery has reached the end of life and, if it determines that the secondary battery has reached the end of life, apparatus. 2. The battery life detection of the secondary battery according to claim 1, wherein the discharging means discharges the fully charged secondary battery until its terminal voltage becomes equal to the discharge end voltage. apparatus.